Theoretical Studies of Copper Oxide Clusters: Prediction of an Electronically Driven Phase Separation in YBa2Cu3Ox

1987 ◽  
Vol 99 ◽  
Author(s):  
L. A. Curtiss ◽  
T. O. Brun ◽  
D. M. Gruen
Keyword(s):  
Phase Diagram ◽  
Phase Separation ◽  
High Temperature ◽  
Copper Oxide ◽  
Superconducting Phase ◽  
Oxygen Stoichiometry ◽  
Molecular Orbital Calculations ◽  
Theoretical Studies ◽  
Two Phases ◽  
Semi Empirical

ABSTRACTOn the basis of semi-empirical extended Hiickel molecular orbital calculations of copper-oxide clusters representing the new superconducting material YBa2Cu3Ox, a phase diagram is proposed which suggests that the 94 K high temperature superconducting phase of YBa2Cu3Ox is characterized by an oxygen stoichiometry near 7.0. The phase diagram predicts that a plateau should exist for Tc in the region x = 0.0 – 0.25 and that in this region two phases are present which are characterized by compositions having oxygen stoichiometries 6.5–6.75 and ca. 7.0.

High-temperature superconductivity in yttrium-barium-copper oxide: identification of a copper-rich superconducting phase

1987 ◽  
Vol 109 (8) ◽  
pp. 2528-2530 ◽  
Author(s):  
Angelica M. Stacy ◽  
John V. Badding ◽  
Margret J. Geselbracht ◽  
William K. Ham ◽  
Gary F. Holland ◽  
...  
Keyword(s):  
High Temperature ◽  
Yttrium Barium Copper Oxide ◽  
Copper Oxide ◽  
High Temperature Superconductivity ◽  
Barium Copper Oxide ◽  
Superconducting Phase ◽  
Barium Copper ◽  
Yttrium Barium

scholarly journals The Strange Metal State of the Electron-Doped Cuprates

2020 ◽  
Vol 11 (1) ◽  
pp. 213-229 ◽  
Author(s):  
Richard L. Greene ◽  
Pampa R. Mandal ◽  
Nicholas R. Poniatowski ◽  
Tarapada Sarkar
Keyword(s):  
Phase Diagram ◽  
High Temperature ◽  
Copper Oxide ◽  
Normal State ◽  
Cuprate Superconductors ◽  
Condensed Matter ◽  
Metallic State ◽  
Final Theory ◽  
Physics Community ◽  
Metal State

An understanding of the high-temperature copper oxide (cuprate) superconductors has eluded the physics community for over thirty years and represents one of the greatest unsolved problems in condensed matter physics. Particularly enigmatic is the normal state from which superconductivity emerges, so much so that this phase has been dubbed a “strange metal.” In this article, we review recent research into this strange metallic state as realized in the electron-doped cuprates with a focus on their transport properties. The electron-doped compounds differ in several ways from their more thoroughly studied hole-doped counterparts, and understanding these asymmetries of the phase diagram may prove crucial to developing a final theory of the cuprates. Most of the experimental results discussed in this review have yet to be explained and remain an outstanding challenge for theory.

scholarly journals Electronic phase diagram of high-temperature copper oxide superconductors

2011 ◽  
Vol 108 (23) ◽  
pp. 9346-9349 ◽  
Author(s):  
U. Chatterjee ◽  
D. Ai ◽  
J. Zhao ◽  
S. Rosenkranz ◽  
A. Kaminski ◽  
...  
Keyword(s):  
Phase Diagram ◽  
High Temperature ◽  
Copper Oxide ◽  
Oxide Superconductors ◽  
Electronic Phase ◽  
Copper Oxide Superconductors ◽  
Electronic Phase Diagram

The Solidification in the Presence of a Metastable Miscibility Gap: The Case of Co-Cu and Co-Cu-X Alloys

2010 ◽  
Vol 649 ◽  
pp. 41-46 ◽  
Author(s):  
Livio Battezzati ◽  
Erik Johnson ◽  
Nini Pryds ◽  
Andrea Penna ◽  
Stefano Curiotto
Keyword(s):  
Phase Diagram ◽  
Phase Separation ◽  
High Temperature ◽  
Critical Temperature ◽  
Melt Spinning ◽  
Enthalpy Of Mixing ◽  
Processing Technique ◽  
Miscibility Gap ◽  
Cooling Conditions ◽  
History Of

Alloys displaying positive enthalpy of mixing demix below a critical temperature. In Co-Cu and related ternaries the miscibility gap is metastable, i.e. it occurs at temperatures lower than the liquidus. In order to study the liquid phase separation high melt undercooling is necessary. This was obtained via rapid solidification techniques using melt spinning and casting in moulding devices, as well as high temperature DSC experiments with samples embedded in a flux. Results are given for Co-Cu, Co-Cu-Fe and Co-Cu-Ni systems. Phase diagrams were optimised using the DSC data. The mechanism of phase separation was investigated by comparing samples produced under different cooling conditions. The hierarchy of microstructures obtained was interpreted accounting for the processing technique and the phase diagram. They constitute a database useful for the interpretation of the thermal history of samples processed in microgravity.

scholarly journals High-temperature superconductivity in sulfur hydride evidenced by alternating-current magnetic susceptibility

2019 ◽  
Vol 6 (4) ◽  
pp. 713-718 ◽  
Author(s):  
Xiaoli Huang ◽  
Xin Wang ◽  
Defang Duan ◽  
Bertil Sundqvist ◽  
Xin Li ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Magnetic Susceptibility ◽  
High Temperature ◽  
High Temperature Superconductivity ◽  
Theoretical Calculations ◽  
Meissner Effect ◽  
Alternating Current ◽  
Superconducting Phase ◽  
Electron Phonon Interaction

ABSTRACT The search for high-temperature superconductivity is one of the research frontiers in physics. In the sulfur hydride system, an extremely high Tc (∼200 K) has been recently developed at pressure. However, the Meissner effect measurement above megabar pressures is still a great challenge. Here, we report the superconductivity identification of sulfur hydride at pressure, employing an in situ alternating-current magnetic susceptibility technique. We determine the superconducting phase diagram, finding that superconductivity suddenly appears at 117 GPa and Tc reaches 183 K at 149 GPa before decreasing monotonically with increasing pressure. By means of theoretical calculations, we elucidate the variation of Tc in the low-pressure region in terms of the changing stoichiometry of sulfur hydride and the further decrease in Tc owing to a drop in the electron–phonon interaction parameter λ. This work provides a new insight into clarifying superconducting phenomena and anchoring the superconducting phase diagram in the hydrides.

Theoretical Studies of Nonbenzenoid Hydrocarbons: 16 π-Electron Systems

1971 ◽  
Vol 49 (17) ◽  
pp. 2840-2849 ◽  
Author(s):  
F. W. Birss ◽  
N. K. Das Gupta
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Theoretical Studies ◽  
Electron Systems ◽  
Consistent Field ◽  
Resonance Energies ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Semi Empirical

Hückel and self-consistent-field semi-empirical π-electron molecular orbital calculations on pentalenoheptalene are reported and the results compared to those of pyrene, acepleiadylene, napth[cde]azulene, and cyclohept[bc]acenaphthylene which contain the same number of π electrons. Resonance energies of all molecules calculated by the methods of Dewar and Whitehead are reported. It is suggested that pentalenoheptalene can be treated as two fused azulene nuclei.

The Phase Diagram of the Two-Dimensional t-J Model from High Temperature Expansions

1992 ◽  
Vol 06 (05n06) ◽  
pp. 585-585
Author(s):  
W.O. Putikka ◽  
M.U. Luchini ◽  
T.M. Rice
Keyword(s):  
Phase Diagram ◽  
Free Energy ◽  
Phase Separation ◽  
High Temperature ◽  
Quantum Monte Carlo ◽  
Helmholtz Free Energy ◽  
Continuation Methods ◽  
Square Lattice ◽  
Cluster Method ◽  
Half Filling

The phase diagram of the 2D t-J model has been investigated using high temperature expansions. Series for the Helmholtz free energy, the inverse compressibility, the chemical potential and the uniform spin susceptibility through tenth order on a square lattice have been calculated using the finite cluster method.1 The series are analytically continued beyond their radius of convergence by Padé and integral approximants. The most accurate extrapolations can be made for the Helmholtz free energy where for J/t≈0.3 and n≈0.9 we can reach T~t/5. We can test the accuracy of the continuation methods by comparing with the 1D results for the boundary of phase separation of Ogata et al.2 In 2D a region of phase separation was found at T=0 for J/t lying above a line extending from J/t=3.8 at zero filling to J/t=1.2 at half filling. No phase separation was found at very small J/t contrary to the earlier suggestion of Emery et al3 which was based on results from exact diagonalisation on 4×4 clusters but in agreement with Quantum Monte Carlo (QMC) calculations on the Hubbard model.4 For very small J/t near half filling where the Nagaoka effect is possible, we find a region of divergent uniform magnetic susceptibility at T=0. However the divergence is very weak when compared with the exponential behaviour expected from a 2D ferromagnet. This might imply a substantially reduced moment which is consistent with the recent QMC estimates of Zhang et al.5

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